GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS, NET, Schedule of Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Goodwill [Roll Forward]
Goodwill as of beginning of year	$ 1,451	$ 1,437
Foreign currency translations	0	14
Goodwill as of end of year	1,451	1,451
Private Client Group
Goodwill [Roll Forward]
Goodwill as of beginning of year	578	564
Foreign currency translations	(1)	14
Goodwill as of end of year	577	578
Capital Markets
Goodwill [Roll Forward]
Goodwill as of beginning of year	275	275
Foreign currency translations	1	0
Goodwill as of end of year	276	275
Asset Management
Goodwill [Roll Forward]
Goodwill as of beginning of year	69	69
Foreign currency translations	0	0
Goodwill as of end of year	69	69
Bank
Goodwill [Roll Forward]
Goodwill as of beginning of year	529	529
Foreign currency translations	0	0
Goodwill as of end of year	$ 529	$ 529